1. Field of the Invention
The invention relates to additives for an electric arc furnace, and more particularly to additives containing metallic oxides which are adapted to be introduced to the furnace.
2. Prior Art
In our patent EP-A-0499779 there is a described and claimed: a method for treating a mixture consisting of solid and liquid waste materials, which contains at least one metal, in particular Fe, and/or its compounds, more especially oxides, whereby the mixture is in a state in which it is unusable or usable only with difficulty, characterised in that the mixture is at least largely homogenised and to is added at least one ultra-fine-grained dry substance comprising fly ash and/or coke, in such quantity, and blended therewith until the resulting mixture is predominantly in the form of briquettes, of which at least part can be supplied for reutilisation in a thermal process; and a method for treating a first mixture consisting of solid and liquid waste materials; which contains at least one metal, in particular Fe, and/or its compounds, more especially oxides, whereby the mixture is in a condition in which it is unusable or usable only with difficulty, characterised in that the first mixture is at least largely homogenised and to it is added at least one ultra-fine-grained dry substance, comprising fly ash and/or coke, in such quantity and blended therewith until the resulting mixture exhibits a nature which enables the classification of the resulting mixture to provide at least one fraction which can be supplied for reutilisation in a thermal process.
The method of the earlier patent works well but when other materials need to be included for addition to the furnace there are disadvantages. Usually one would mix a baghouse dust (which contains valuable recoverable toxic metals such as lead and zinc) with the mixture and then process the blend as described. The need to blend the dust with the mixture means that very large mixing plant is required, which aggravates the capital cost. Because there is much loose dust in the atmosphere there is a health hazard for operators.
GB-A-928084 discloses mixing together metallic oxide, a carbonaceous reducing agent, a hydraulic binding agent and water to form pellets which are allowed to harden without added heat. Storage takes place over one to seven days, but the conditions of storage are not identified. WO 96/31630 discloses a similar process using waste materials. Again the conditions of storage are not mentioned.
It is one object of the invention to provide a method of forming a substantially dry injectable particulate composition from waste materials in a more convenient and economic way.